Abstract: A process for producing calcine products includes dead roasting a metal sulfide concentrate having a low sulfur content. The concentrate is roasted in a circulating fluidized bed at a temperature of about 950 to 1050° C. A waste gas of the fluidized bed is passed through at least one of a recuperator and a Venturi drier so as to respectively provide at least one of a preheating of at least a portion of air fluidizing the fluidized bed and a drying of at least a portion of the concentrate to be roasted. The calcine product obtained in the fluidized bed with a sulfur content of less than 1 wt-% is provided for further processing.

Abstract: A method for dividing a stream of solids includes discharging the stream of solids via a first downer. The stream of solids are fluidized at a bottom of the first downer by supplying a first conveying gas. By the first conveying gas, a part of the stream of solids are conveyed to a top of a first riser branching off from the first downer. A remaining part of the stream of solids are discharged via a second downer adjoining the first downer. The remaining stream of solids are fluidized at a bottom of the second downer by supplying a second conveying gas. By the second conveying gas, a part of the remaining part of the stream of solids are conveyed to a top of a second riser branching off from the second downer.

Abstract: A method for controlling at least one of a level of solids and an inventory of solids in a solids tank includes withdrawing a stream of solids from the solids tank via a downer. The stream of solids withdrawn from the solids tank is fluidized at a bottom of the downer by supplying a conveying gas so as to convey the withdrawn stream of solids upward via a riser branching off from the downer, a size of the conveyed stream of solids being adjusted by the supplying of the conveying gas. At least one of the level and the inventory of the solids in the solids tank is used as an adjustment variable of a control circuit and a volume flow of the conveying gas is used as an actuating variable of the control circuit.

Abstract: The starting material is a vanadium-containing residue, which contains at least 5 weight percent carbon on an anhydrous basis. The residue is thermally treated in a furnace a) at temperatures from 400.degree. to 700.degree. C. under an oxidizing atmosphere and an O.sub.2 partial pressure of at least 10.sup.-4 bar, measured within the region which is occupied by the residue, and/or b) at temperatures from 500.degree. to 1300.degree. C. under an O.sub.2 partial pressure not in excess of 10.sup.-2 bar, measured within the region which is occupied by the residue. A solids mixture which contains at least 5 weight percent vanadium oxide is withdrawn from the furnace. A multiple-hearth furnace or a rotary kiln or a fluidized bed reactor containing a stationary or circulating fluidized bed may be used as a furnace for the thermal treatment.